234 BACTERIAL DISEASES OF PLANTS 



in gelatin plates (X125) are irregularly spherical, often more 

 or less clumpy, uniformly granular and with sharp margins 

 which tend to become hazy. Sometimes the buried colonies 

 send out colorless root-like growths (Fig. 182). Stab cultures 

 liquefy first at the surface but eventually throughout (Fig. 183A). 

 There is a fragile imperfect white pellicle and a copious white 

 precipitate, the fluid becoming strongly alkaline. 



Peptonized beef bouillon clouds very rapidly, especially 

 when neutral to phenolphthalein (in 6 hours at 30°C., when in- 

 oculated with a 1-mm. loop). If undisturbed there is formed 

 a very thin imperfect pellicle which shakes down readily leaving 

 a scanty interrupted rim, easily washed away. The white 



::#-. 



' ■ . '■^.. 



• - ■ ' ' ' K ' ■ 



Fig. 176. — Flagellate rods of Bacillus carotovorus. From a 2-day agar streak. 

 Van Ermengem's silver nitrate stain. In the upper right there are two bacterial 

 rods lying together. X 1000. 



precipitate is not copious. It (3a) gives in +15 peptone 

 bouillon a heavier clouding than B. phytophthorus. Growth 

 in Dunham's solution is feeble. Growth in Uschinsky's solu- 

 tion is abundant and long-continued and the fluid remains 

 more or less acid throughout: there is a copious precipitate 

 (15 or 20 times that in bouillon), but only a deUcate easily 

 fragmented pellicle. In milk a curd separates about the fourth 

 day. It has the odor of cheese curds and there is little or no 

 peptonization of this curd. Litmus milk is reddened and the 

 litmus is, or may be, subsequently reduced. Other pigments 

 are reduced, such as methylene blue (in Dunham's solution 

 with grape sugar, not without). 



